The proposed research is designed to characterize the etiology and pathogenesis of a new form of slowly progressive hereditary retinal degeneration which occurs in Wag/Rij rats and to evaluate its suitability as an animal model for hereditary retinal degeneration of humans. The research is divided into 4 conceptual areas. The first is to characterize the development of retinal degeneration histologically, ultrastructurally, ophthalmoscopically and electroretinographically. The second is to determine the effect of ambient light on the development of retinal degeneration by raising rats in darkness and comparing retinal changes with retinal changes in rats raised in ambient light. The third is to study the rate of renewal of photoreceptor outer segment material at various stages of the disease by autoradiography. The fourth is to clarify the mode of inheritance of the disease by breeding experiments.